1. Field of the Invention
The present invention relates to a switching circuit for a reactive power compensation device having in-line assembled capacitors as well as a circuit for closing and opening phase conductor switches with which the reactive power compensation device can be switched on and off during zero current passage to the phase conductors upon application of control signals.
2. Description of the Related Art
A switching circuit of this type is known by the name of RTPFC-(Real Time Power Factor Controller-) system from a brochure by the firm ELSPEC Engineering Ltd., in Tel-Mond, Israel, circulated in the spring of 1994. With this switching circuit, a reactive power compensation device can be switched using electronic switches during zero current passages of the compensation capacitors, which can be detected by a current measuring unit. Switching between various compensation groups of the reactive power compensation device occurs within a few seconds in order to avoid great switch-on surges. The number of compensation groups required depends on the frequency of switchings per time unit as well as on the discharging of the compensation capacitors of the individual compensation groups.
This switching circuit has the drawback that if big energy consumers, such as for example construction crane engines, are switched in rapid succession, a multiplicity of compensation groups having relatively short discharge constants are needed. Thus, in addition to disadvantageous high energy consumption due to the discharge of the switched off compensation capacitors, expensive in-line assembly of the switchable compensation groups on the reactive power compensation device is required.